An impressive eyepiece for sure.A serious evaluation of the target with the radial line of Saturns showed a deterioration (slight!) in the focus only right at the edge (maybe 48 degrees from center!). The focus on the plate with the metal shavings showed a little deterioration somewhat closer in, maybe at 45 degrees off center.But that's amazing!For sure, I'd like to spend a leisurely night under the stars with one in a Paracorr in my 12.5" and compare it to the T6 Nagler.Sigh. I guess I'll just have to wait.Like Daniel, I was amazed at how light it was. The 31 Nagler feels like it weighs twice as much.Now if TeleVue only charged by the pound!

An impressive eyepiece for sure.
A serious evaluation of the target with the radial line of Saturns showed a deterioration (slight!) in the focus only right at the edge (maybe 48 degrees from center!). The focus on the plate with the metal shavings showed a little deterioration somewhat closer in, maybe at 45 degrees off center.
But that's amazing!
For sure, I'd like to spend a leisurely night under the stars with one in a Paracorr in my 12.5" and compare it to the T6 Nagler.

My goodness Don, and I thought I was critical, but at least you acknowledged that. I have to give Televue credit where it is due. As you well know, there are always going to be some slight inherent aberrations and trade offs. It's simply impossible to correct for them all. I personally found the Ethos to be WELL within the perameters of what I would consider excellent edge correction, not to mention that this was accomplished with an AFOV of 100 degrees. I love Naglers too but the Ethos is simply in a whole different class. I could tell the very second I looked throught it that this industry is seriously in for a surprise. Maaaaaan, now if I could just bino a set of them, I'd literally be swimming in space. BTW, I think Televue mentioned that they may not be able to get an Ethos much over 20mm's for technical size reasons. Either way, I'm very pleased with the 13mm focal length and I'm itching to get one as soon as possible. The Milky Way will be absolutely astonishing through an NP101 using the Ethos.

I know that I'm very critical with Televue sometimes but I was so humbled when I looked through this eyepiece. I mean really think about this. Nobody has done anything like this in the amateur industry, ever! I realize that Al basically oversaw the design and construction of it but he really is the driving force behind it and sometimes I have to look at the big picture and seriously realize that Al is a passionate individual. I mean this guy is literally in love with the night sky, it's not just a business to him. He will go on for hours viewing the night sky and I love the man for it. I know plenty of people in this business who could care less about the night sky and I try to avoid that breed sometimes. Honestly, what other company has this much variety in their eyepiece line?

thanks for the great review
forgive the silly question
but what does "warm" mean in this context?
(i won't tell al)

Oh please don't bring it up. I'm seriously gonna be in more trouble. I can just hear Al screaming coffee tones. I may have to get on the next flight off this planet. Believe me if you have to ask, it's not worth concerning yourself over it

There's a reason every eyepiece in my case has green writing on it. Over the years, I've come close to owning every one of them. The three I've never owned are: 26T5 Nagler, 20T5 Nagler, and 16T5 Nagler.Radians were the only series that I lost. I had the complete set with my 6" f/5 but they burned up in a fire in Malibu in 1993. It's OK--they were replaced with eyepieces better-suited for the 8" SCT that replaced the 6".